Treatment of iron or steel



Patented May 20, 1930 UNITED STATES I Y Cross Reference .Qusasas I PATENT orrics m! B. THEWS, OI DREXEL HILL, AN'D 'J'QSEPH S. CARLITZ, OF PHILADELPHIA, PENNSYLVANIA; SAID CABLITZ LSSIGNOB TO SAID THEWS TREATMENT OF IRON OB STEEL Io Drawing.

This invention relates to a process for reducing the dissolution of iron and steel during the removal. of iron oxide or scale m ickling baths of lhe methods disclosed herein are also useful in preventing corrosion of iron and steel containers of such' acids.

Heretofore it has been customary to use various inhibiting agents in the pickling baths to prevent pitting or etchin of the surface of the iron or steel. These su stances have been more or less successful in the attainment of such results, the best of these inhibitors so far used apparently being the 5 substitution products of no rm al thiourea of which the ditolyl derivatives are the most effective.

We have discovered that the normal selenourea and normal tellurourea derivatives go are generally superior to the corresponding derivatives of normal thiourea in preventing the solution of iron or steel in acidic liquids such as picklin baths. The use of such derivatives is claimed in an application Serial Number 412,565, filed of even date herewith. We have further found, however, that derivatives of pseudo thinurea pseudosgrlgipnrea, and pseudo-tellurou re equiva ent or superior as inhi itors to the corremal selenourea and normal tellurourea. It is accordingly the object of the present invention to improve the processes heretofore used by the use as inhibitors of the derivatives of the above mentioned pseudo-ureas.

The attainment of the object outlined above and more specific objects of the invention will be clear from the followin descri tion. The pseudo-derivatives whic are ou nd to have the more efiective inhibiting action have the following general formula:

' NR:C(X':R' NR;

(W in which X represents W, selenium, or tellurium, R represents ydrogen, or an alkyl, aryl or acyl group, and R re resents an alkyl, 1 or acyl group; this de 'tion including su stances having the same general formula 60 in which a bivalent alkyl, aryl or acyl absponding derivatives of nwllihi rea, nora single linkage wherebysa cyclic compound Application ma December 7, 1929. serlaljl'o. gases.

stituent group, such as an ethylene group, replaces R' and an R, be? connected to both a nitrogen atom and the atom.

As exam les of suitable alkyl groups, there may cited methyl, ethyl, propyl, butyl, amyl, etc., propyl, butyl, amyl and higher radicals being of any of the various isomeric t es, such as normal, iso-, tertiary, etc. Substituted alkyl groups may also be used, in which, for example, one or' more hydrogen atoms are replaced by amino, sulphonic, nitro, or other The ar 1 groups may e joined to the nitrogen or atoms either at the nucleus or side chain. Of the first type, phenyl, tolyl, xylyl, or naphthyl, etc. are examplles. Th

e unct10n to the nitrogen or sulp ur, selenium or tellurium atoms may take place at any of the unsubstituted carbon atoms. Of the second type, benzyl is thebest example. Here again there may be various groups replacing the hydrogen atoms in either the nucleus or side chains.

The acyl grou s may be formyl, acetyl, propionyl, benzoy phthalyl, succinyl; etc., or substituted derivatives thereof.

If two substituent groups are present there maybe obtained (11, 41 ,or 0, v) derivatives. In view' of the fact t at the substituted positions are not symmetrical, two difierent sub stituent groups may form two difierent n w etc. derivatives. For example, n-methyl ip benzyl selenourea is difierent from il-methyl n-benzyl selenourea.

Similar considerations will indicate the numerous isomeric derivatives producible by the presence of either three or four substituents. The resence of stereoisomers is readilfy explaina le by reference to the structural ormula.

There ma also be used derivatives in which one o the nitrogen atoms and the X atom are joined to a single radical, each by is obtained. The radica in these cases may be. either alkyl, aryl, or acyl. I

It will be understood that where the term alkyl is used, it is in. a broad sense so as to include not only the alkylene groups, such as ethylene, but also heterocyelic derivatives Examiner A rearrangement of the molecular structuretakes place during such reaction whereby a pseudo derivative is formed.

In a general way it may be said that the operative substances are re general formula above in w ich one or more of the Rs represent an organic radical or hydrogen, and in which X represents S, Se or Te. It appears that the inhibiting action to a greater or less degreeis characteristic of this class of compounds.

The mechanism of the rocess involved in using these substances is similar to that usually used. 'The pickling solution may contain sulphuric or other suitable acidic materials such as are now used in eflective concentrations. For example, approximately 10% sulphuric acid solution in water may be used. To such pickling solution up to approximately 1% of one of the inhibitin agents isadded. The pickling is then e fected -'n the usual fashion by submerging the iron or steel articles in the solution either at ordinary or elevated temperatures. cases where it is desired to protect a tank against acid which is contained therein, the inhibiting agent is added to the acid.

4 Of the various derivatives the alkyl and aryl are generally found to behest; the acyl derivatives are less efiective. The best derivatives appear to be those in which a substituent group is attached to the X atom in the #1 position, although operative inhibitors are obtained if the substituent group or groups enter the n and v sitions. In gen- -er'al the pseudo-thio-, se eno, and telluroderivatives are either equivalent or superior to the normal derivatives containing similar substituents. Of the three groups, the seudo-thiourea derivatives appear most efective.

For convenience in handling the inhibiting substances in the small quantities necessary in a pickling bath, it may be desirable to mix 'them with a large proportion of a carrier the seleno I substance which may be of such nature as to assist the pickling action, for example, sodium chloride or sodium bisulphate. Mixtures of various inhibiting agents may also be used. a

The various derivatives referred to are best pretplared by the general methods well known to e art. In (general it may be stated that tellurourea derivatives are resented by the.

prepared similarly to the correspondin pseudo-thiourea derivatives althou hspecifi inethods of preparation are well own to the art. In view of the fact that the preparations of the derivatives form no part of the instant invention, they have not been discussed in detail.

What we claim and desire to protect by Letters Patent is:

1. An aqueous solution of a non-oxidizing acid capable of dissolving iron oxides to which has been added an inhibitor comprising an organic pseudo-substitution product of NH: C(XH)-NH in which X represents S, Se or Te.

2. An a ueous solution of a non-oxidizing acid capa le of dissolving iron oxides to which has been added an inhibitor comprising an organic pseudo-substitution product of thiourea.

3. An aqueous solution of a non-oxidizing acid capable of dissolving iron oxides to which has been added an inhibitor comprising an organic pseudo-substitution product of NH: C(SHg-NI-L, in which the hydrogen attached to su phur is replaced by an alkyl,

aryl or ac l grou 4. An agueous Solution of a non-oxidizing acid capable of dissolving iron oxides to which has been added an inhibitor comprising a substance having the general formula N :C(SR')-NR in which R represents hydrogen or an alkyl, aryl or acyl group, and B. represents an alkyl, aryl or acyl group.

5. An aqueous solution of a non-oxid1zing acid capable of dissolving iron oxides to which has been added an inhibitor comprising p-benzyl thiourea.

6. The process of pickling iron and steel products which consists in treating said products with an aqueous solution of a non-oxidizing acid capable of dissolving iron oxides to which has been'added an inhibitor comprising an organic pseudo-substitution product of NH: C(XH)-NH,, in which X represents S, Se or Te.

7. The process of pickling iron and steel products which consists in treating said products with an aqueous solution of a non-oxidizin" acid capable of dissolving iron oxides to which has been added an inhibitor comprising an organic pseudo-substitution product of thiourea.

8. The process of pickling iron and steel products which consists in treating said products with an aqueous solution of a non-oxidizing acid cagzble of dissolving iron oxides to which has en added an inhibitor comprismg an organic pseudo-substitution product of NH: C(SPQ-NH in which the hydrogen attached tosu phur is replaced by an alkyl,

.aryl or acyl group.

252. COMPOSITIONS.

in acid capable of dissolving iron oxides to which has been added an inhibitor comprismg a substance having the general formula NR C(SR')-NR,, in which R represents hywhich has been added an inhibitor compris-.

in \p-benzyl thiourea. I

la testimony of which invention, we have hereunto .set our hands, at Philadelphia, Pennsylvania, on thisGth'day of December,

KARL B. THEWS. JOSEPH S. CARLITZ.

Cross Reference Examiner 

